Various types of optical displays are commonly used in a wide variety of applications. Included among these various types of displays Liquid Crystal Displays (LCDs). LCDs are typically direct view displays or projection displays. In the direct view approach the image is created and viewed directly on the LCD with a light source opposite the view side. In the projection approach, this LCD image is projected through an optical lens system on to a screen. In the case of a rear projection TV the image is projected on to a diffuse screen. In the case of a Head Up Display (HUD), the image is projected on a partially reflective screen.
One important performance parameter in projection displays in general, and HUDs in specific, is the range of luminance that can be provided by a projection display. In many applications it is critical that a display make information clearly visible in a wide variety of ambient light conditions. For example, a display used in an avionics system will need to display information to the pilot under lighting conditions that can range from near total blackness to the extreme glare created by facing directly into daytime sunlight. Thus, a display used in an avionics system must have the ability to provide a high brightness image. Without a sufficiently high brightness, a viewer of the display may be unable to easily read information from the display in high ambient light conditions. An additional challenge for the HUD type displays is the image is only partially reflected on a see-through screen. This partial reflection maybe only 15% of the projected image, hence placing higher brightness requirements on the display backlight.
To achieve high brightness is projection displays previous systems have relied upon high energy lamps such as high pressure arc lamps. While high pressure arc lamps provide high brightness, they can also generate significant heat. This heat must be dissipated away from components or it can interfere with their reliable operation. To dissipate this heat, significant area may be required to provide heat sinks or another heat transfer path away from critical components. Additionally, high pressure arc lamps may have increased explosion potential when seals rupture and have difficulty in dimming over a wide range. Thus, the use of high pressure arc lamps can be undesirable where the size of the display is limited, and where reliability and safety is a primary concern
Accordingly, it is desirable to provide an improved lamp system that can provide high luminance output in a compact size for use in LCD displays. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.